This application is related to Japanese Patent Application No. 2002-83457 filed on Mar. 25, 2002, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a sheath liquid for a particle analyzer.
2. Description of Related Art
In recent years, there have emerged apparatus using a sheath flow system for discriminating and/or analyzing cells or fine particles, and the discrimination and analysis of biological samples such as blood, urine and the like are more and more highly automated and are speeded faster and faster.
The sheath flow system is a technique for obtaining the count of and morphological information about cells or particles. The cells or particles, as they are or in the form of a suspension or a diluted sample, are enveloped in a stream of a sheath liquid and are passed one by one at an optimal flow amount and flow velocity in a flow cell of a flow cytometer. The count and morphological information are obtained by detecting an electrical or optical pulse generated by the cells or particles when passing by a detecting section in the flow cell.
For example, a sample containing object cells, particles and the like is lead by the steam of the sheath liquid to a detecting section, where the cell or particles are irradiated with a laser beam from a laser light source via a lens for focusing light emitted from the light source. The emitted light is stopped by an emitted light stopper, and only forward scattered light from the cells or particles is detected by a forward scattered light detector via a lens for detecting forward scattered light. On the other hand, side scattered light is detected by a side scattered light detector via a lens for detecting side scattered light. Voltage values detected by the detectors are input to an analyzer, which produces a scattergram by the forward and side scattered light based on the voltage values, displays the scattergram on a display and counts the cells and particles.
In the case where the laser light source is a red light source such as a He-Ne laser, a semiconductor laser or the like, no problems are observed with samples like blood which are diluted at a high dilution factor, but accurate analysis results cannot be obtained with samples like urine which are used as they are or which are diluted at a low dilution factor.
More particularly, in the case of a sample like urine intrinsically having a high refractive index, the sample and the sheath liquid have greatly different refractive index at a wavelength near red. Consequently a baseline of a forward scattered light signal fluctuates, and a population may appear in a scattergram as if a lot of particles existed although particles are not present in the sample. Therefore, particulate components in the sample cannot be counted accurately.
An object of the present invention is to provide a sheath liquid for a particle analyzer that allows a sample having a high refractive index to be analyzed accurately even with use of a red light source.
The present invention provides a sheath liquid for use with a particle analyzer having a refractive index of 1.3340 or more (preferably 1.3380 to 1.3450) at the wavelength of sodium D line at 25xc2x0 C.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.